docs: def handle_set_citation_double(self, line: str, position: int, tokens: ParseResults) -> ParseResults:
          """Handle a ``SET Citation = {"X", "Y"}`` statement."""
          values = tokens['values']
  
          if values[0] == CITATION_TYPE_PUBMED and not is_int(values[1]):
              raise InvalidPubMedIdentifierWarning(self.get_line_number(), line, position, values[1])
  
          self.citation = dict(zip((CITATION_TYPE, CITATION_REFERENCE), values))
          return tokens